Granular convection and the Brazil nut effect in reduced gravity

Abstract

We present laboratory experiments of a vertically vibrated granular medium consisting of 1-mm-diameter glass beads with embedded 8-mm-diameter intruder glass beads. The experiments were performed in the laboratory as well as in a parabolic flight under reduced-gravity conditions (on Martian and Lunar gravity levels). We measured the mean rise velocity of the large glass beads and present its dependence on the fill height of the sample containers, the excitation acceleration, and the ambient gravity level. We find that the rise velocity scales in the same manner for all three gravity regimes and roughly linearly with gravity.

Timescale of asteroid resurfacing by regolith convection resulting from the impact-induced global seismic shaking

“…Using an experimentally obtained scaling relation, they found that the convective velocity is scaled by g 0.97 . While the intruder's rise velocity (BNE rate) and convective velocity are different quantities, Yamada and Katsuragi (2014) is roughly consistent with Güttler et al (2013). However, the reason of difference between Güttler et al (2013) and Matsumura et al (2014) remains unclear.…”

“…While the intruder's rise velocity (BNE rate) and convective velocity are different quantities, Yamada and Katsuragi (2014) is roughly consistent with Güttler et al (2013). However, the reason of difference between Güttler et al (2013) and Matsumura et al (2014) remains unclear. In any case, all these experimental and numerical results suggest that the granular convection can occur with very low velocity even under the microgravity condition.…”

“…Recently, the gravity dependence of granular convective motion has been investigated on the basis of laboratory experiments (Murdoch et al, 2013b,c,a;Güttler et al, 2013;Yamada and Katsuragi, 2014) and numerical simulations (Tancredi et al, 2012;Matsumura et al, 2014). Murdoch et al (2013b,c,a) investigated the gravity dependence of the velocity of shear-driven convective motion by using the parabolic flight method.…”

“…They reported that the convective velocity is significantly reduced under the microgravity condition while it is enhanced under the high-gravity condition. Güttler et al (2013) also performed an experiment of convection-driven BNE using the vibrated granular bed on parabolic flights. They found that the rise velocity of an intruder in the vibrated granular bed is roughly proportional to the gravitational acceleration g. Tancredi et al (2012) numerically computed the threshold velocity v th to induce BNE and reported v th ∼ g 0.42 .…”

Small Solar System Bodies as granular media

“…Moreover, the vibration induced convection in the container creates a wide upward flow in the central part of the system but only a thin downward flow along its boundaries so that all sorts of grains can rise to the surface but only small particles can dive back to the bottom. Investigations during parabolic flights (Güttler et al 2013) have shown that BNE can be observed in low gravity conditions even though its driving mechanisms are strongly linked to gravity, although sometimes in a complex manner (Staron 2016). This result consolidates the theory that certain surface structures on asteroids are created by this kind of segregation (Miyamoto et al 2007).…”